His wife, Amelie, was in their home on the outskirts of Paris, preparing to evacuate.

His elder son, Jean, was serving as a mechanic in the reeling French army. His younger son, Pierre, was counting the days until he was old enough to enlist. The day came, from his heartsick father’s point of view, all too soon.

And what of Marguerite, his beloved daughter from an earlier relationship, his stalwart assistant, his model, his confidante?

Back when she was 6, Marguerite had contracted croup or diphtheria. Her breathing became so obstructed that a surgeon was forced to slit open her throat while Matisse held her down on a table.

The emergency tracheotomy left her with a three-inch scar that she covered for the rest of her life with a black ribbon.

Matisse never quite recovered from that early ordeal. He was exceptionally close to Marguerite. She was, according to Matisse’s biographer Hilary Spurling, “sensitive and highly strung like her mother.” But she also had “her father’s passionate will, his courage and pride, his horror of compromise, and his stubborn sense of duty.”

In 1918, with all the balls of life up in the air, Marguerite was again ill, and in need of continual expert medical supervision. In Nice, where Matisse had been based since the previous year, the facilities were inadequate. Qualified surgeons had been dispatched to the front.

So Matisse prepared to move with Marguerite to a residence as close to the front, and its surgeons, as he could get. He took her to Paris with that desperate plan in mind.

The French army, meanwhile, launched a counterattack from Amiens, the Germans were pushed back, Paris saved.

In the midst of all this, Matisse painted several portraits of Marguerite.

In her weakened state, shortly before she was admitted to hospital, she was dressed in chic outfits designed by Germaine Bongard and various hats from a favorite milliner on the rue Royale.

This one, a toque made from the beautiful blue feathers of the crowned pigeon, was adorned with an ostrich feather. Its arabesques are echoed by the lines uniting Marguerite’s nose and eyebrows ­— that classic Matissean motif.

Matisse paints the blue-black toque and the green-black background with a swishy touch reminiscent of Manet, a touchstone for Matisse in these years. The striations on her dress, which Matisse scratched in with the back of his brush, relieve the monotony of the large expanse of black. The orange chair, ignited by the particolored dabs on the cushion, brings the whole painting to life.

Matisse’s love for his frail but resilient daughter is palpable in every inch of this painting. But so is his ability to go on concentrating on what he was born to do, even under extreme duress.

Sebastian Smee can be reached at ssmee@globe.com.

Correction: Because of a reporting error, an earlier version of this column mischaracterized the marital status of the mother of Henri Matisse’s daughter, Marguerite. The mother and Matisse were not married.

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